Not simply tracks but the entire arcade game contained within 'F-Zero GX.'
Back in 2003, Nintendo and Sega collaborated to release two 'F-Zero' titles, one for arcades and one for home. While 'F-Zero GX' for the GameCube with its steep challenge found a dedicated fan base in the US, few would ever have the opportunity to try out the distinct arcade version.
Those players who managed to take a GameCube memory card with a 'F-Zero GX' save on it to an 'F-Zero AX' arcade cabinet and back again could unlock the arcade version's tracks at home, which was pretty slick if rarely accomplished outside of Japan.
What has been discovered now through the use of Action Replay/Gameshark devices is that not only are the arcade tracks contained on the GameCube disc, but actually the entire arcade version.
After ten years in the market and in homes, only now has this hidden gem been discovered. The necessary codes can be found at Retrocollect.
Source:Retrocollect via Destructoid